1. Field of the Invention
The present invention relates to a multi-layered printed wiring board used for electronic devices and the production method thereof. More particularly, the present invention relates to a plating method for electrically connecting circuit conductor layers to one another through via holes formed in an insulating resin layer, after alternatively laminating the circuit conductor layer and the insulating resin layer, the production method for a multi-layered printed wiring board including the placing method, and the multi-layered printed wiring board produced by such methods.
2. Description of the Related Art
The conventional production methods for a multi-layered printed wiring board are described in, for example, Japanese Laid-Open Patent Publication No. 4-148590. The Japanese Laid-Open Patent Publication No. 4-148590 discloses a production method for a multi-layered wiring board comprising the steps of forming a first circuit conductor layer by etching a copper foil provided on the top and bottom surfaces of an insulating substrate; forming an insulating resin layer having photo via holes on the first circuit conductor layer; chemically roughening the surface of the insulating resin layer after forming through-holes in the insulating substrate; and forming a second circuit conductor layer on the roughened surface of the insulating resin layer by an electroless copper plating method and an electrolytic copper plating method so as to electrically interconnect the first and second circuit conductor layers to each other through the photo via holes and the through-holes.
In this conventional method, the chemical etching treatment mainly using potassium permanganate is performed as a pretreatment for forming the electroless copper plating layer on the insulating resin layer. The chemical etching treatment has an objective to form minute irregularities on the surface of the insulating resin layer by chemical etching, thereby improving the adhesion of the electroless plating layer to the Insulating resin layer.
The above-mentioned conventional technique, however, still cannot attain sufficient adhesion between the insulating resin layer and the electroless copper plating.
Further, the reliability of the electrical connection within the blind via holes and the through-holes by the electroless plating is not sufficient.